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JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2005

  • question_answer
        From a building two balls A and B are thrown such that A is thrown upwards and B downwards (both vertically). If\[{{v}_{A}}\]and\[{{v}_{B}}\]are their respective velocities on reaching the ground, then

    A)  \[{{v}_{B}}>{{v}_{A}}\]                

    B)  \[{{v}_{A}}={{v}_{B}}\]

    C)  \[{{v}_{A}}>{{v}_{B}}\]

    D)  their velocities depends on their masses

    Correct Answer: B

    Solution :

                    From conservation of energy, potential energy at height h =K.E. at ground Therefore, at height h, P.E. of ball A                 \[P.E.={{m}_{A}}gh\] K.E. at ground \[=\frac{1}{2}{{m}_{A}}v_{A}^{2}\] So,          \[{{m}_{A}}gh=\frac{1}{2}{{m}_{A}}v_{A}^{2}\] \[{{v}_{A}}=\sqrt{2gh}\] Similarly,    \[{{v}_{B}}=\sqrt{2gh}\] Therefore,   \[{{v}_{A}}={{v}_{B}}\]


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